Flapper gate forming tube assembly for packaged produce containers

ABSTRACT

A system for reducing metal and product-in-seal contamination in a package of produce product is provided. The system includes a tube and a flapper gate assembly. The flapper gate assembly is connected to the top of the tube, and includes a pivot and a flapper gate. The pivot is positioned outside the tube. The flapper gate is positioned inside the tube and is connected to the pivot. The flapper gate is configured to regulate product flow in the tube by rotating around the pivot when the pivot is rotated.

BACKGROUND

1. Field

This application relates generally to a system for reducing metal contamination and product-in-seal failures in packaged produce containers and, more specifically, to interrupting or regulating flow of fresh produce into a bag using a forming tube assembly flapper gate device.

2. Description of the Related Art

A protective container, such as a polypropylene bag, can be used to preserve the quality of packaged produce product while it is being transported and stored before consumption. The container isolates fresh produce contents from environmental elements that can cause damage or premature spoilage. The container also protects the produce from contaminates and physical contact by forming a physical barrier. The container may also help to preserve the produce by maintaining environmental conditions that are favorable to the produce. For example, a protective container may reduce oxygen consumption and moisture evaporation by trapping a pocket of air around the packaged produce. Properly sealing the container is essential to maintaining the desired internal atmosphere and extending shelf life of the product.

One common protective container is the polypropylene bag, which is flexible, durable, and allows for the visual inspection of the product by the manufacturer, retail grocer, and end user. Polypropylene bags can be produced at a relatively low cost, and are compatible with numerous high-volume automated packaging techniques. For example, a vertical form, fill, and seal (VFFS) packaging process can be used to place fresh produce into polypropylene bags as they are formed. In a VFFS packaging process, a partially enclosed cavity is created by folding or sealing the polypropylene film to form a pocket. The fresh produce is placed in the pocket and then sealed as the pocket is formed into a fully enclosed polypropylene bag. In an alternative process, a polypropylene sleeve can be used to form an open-ended pocket. Fresh produce is placed in the pocket and the open end (or ends) are sealed using sealing jaws. While these two examples have been discussed, various other techniques exist for packaging fresh produce.

As a typical result of these packaging processes, ambient air is trapped in the sealed polypropylene bag. For some types of produce, the oxygen content of ambient air may be harmful to the longevity of a retail produce product. For example, if the produce includes fresh lettuce leaves, the oxygen content of ambient air (having oxygen content of approximately 20 percent) can cause a polyphenoloxidase reaction that degrades the quality of the lettuce leaves. The shelf-life of packaged lettuce leaf may be significantly extended if it is packaged in a protective container that maintains oxygen levels between 1 percent and 9 percent. The container must be properly sealed to maintain the desired oxygen levels.

Alternatively, air can be removed from a partially enclosed polypropylene bag to reduce the amount of oxygen by applying a vacuum or by heat shrinking the bag to conform to the dimensions of the produce. However, some fresh produce products, including lettuce leaf and other leafy vegetables, are too delicate to withstand either a vacuum sealing or heat shrinking process. As a result, most packaging processes for leafy vegetables trap at least some volume of air in the polypropylene bag. In fact, in some cases, a slight positive pressure of air inside the bag may even be desirable as it provides some mechanical cushioning for the produce product by slightly expanding the walls of the polypropylene bag away from the leafy vegetable contents.

A leak in the seal of the bag can prevent the desired oxygen level from being maintained and cause the bag to lose internal pressure. Therefore, it is desirable to properly seal the protective container to maintain the desired internal atmosphere.

In addition to the integrity of the seal, metal contamination is another concern when using a mechanical device such as a VFFS machine to package produce. As a typical result of using a mechanical device in the packaging process, components such as loose or misaligned nuts and bolts can fall into the protective container and contaminate the packaged product. Metal shavings from dynamic portions of the machine can also contribute to contamination. Thus, it is also desirable to reduce the risk of metal contamination due to the failure of mechanical components in a packaging system.

SUMMARY

One exemplary embodiment includes a system for reducing metal and product-in-seal contamination in a package of produce product. The system includes a tube, a partially enclosed cavity, a flapper gate assembly, and a sealing assembly. The tube is positioned substantially vertically, and has a top, bottom, inside, and outside. The partially enclosed cavity contains the produce product, and has a cavity opening positioned below the bottom of the tube. The flapper gate assembly is connected to the top of the tube and includes a linkage assembly, a pivot assembly, and a flapper gate. The linkage assembly has a bracket attached to the outside of the tube and a linkage arm connected to the bracket in a fixed position relative to the tube. The pivot assembly is positioned outside the tube and is attached to the linkage arm. The pivot assembly includes an actuator, a piston rod, a pivot arm, and a hinge. The actuator is configured to drive the piston rod, and the piston rod is connected to the pivot arm, which rotates around the hinge when the piston rod is driven. The flapper gate is positioned inside the tube and is connected to the pivot arm via the hinge. The flapper gate is configured to rotate around the hinge when the pivot arm is rotated to regulate product flow in the tube. The sealing assembly is configured to seal the partially enclosed cavity to form a fully enclosed package.

In some embodiments, the flapper gate assembly is connected to a vertical form, fill and seal (VFFS) machine. In some embodiments, the package is a polypropylene bag. In some embodiments, the flapper gate is a single-piece stainless steel gate.

One exemplary embodiment includes a method of reducing metal and product-in-seal contamination in a package of produce product. The method includes the steps of loading the produce product into a tube, opening a flapper gate located at the top of the tube to allow the produce product to flow through the tube into an opening of a partially-enclosed cavity positioned below the tube, closing the flapper gate to stop the flow of produce product through the tube, and sealing the partially enclosed cavity to produce a fully enclosed package containing the produce product.

In some embodiments, the method includes the step of collecting the produce product inside the tube using the flapper gate. In some embodiments, the partially enclosed cavity is sealed when the partially enclosed cavity is determined to be full. In some embodiments, the method is implemented as part of a VFFS packaging operation.

DESCRIPTION OF THE FIGURES

FIG. 1 depicts a process for packaging produce in a packaged food container.

FIGS. 2A-C depict components for packaging produce in a packaged food container.

FIG. 3 depicts an exemplary process for reducing the amount of product-in-seal in a packaged food container.

FIGS. 4A-C depict exemplary components for reducing the amount of product-in-seal in a packaged food container.

FIG. 5 depicts an exemplary flapper gate assembly

FIG. 6 depicts measured product-in-seal failures of flapper gate assemblies and non-flapper gate assemblies.

The figures depict one embodiment of the present invention for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein can be employed without departing from the principles of the invention described herein.

DETAILED DESCRIPTION

The following description sets forth numerous specific configurations, parameters, and the like. It should be recognized, however, that such description is not intended as a limitation on the scope of the present invention, but is instead provided as a description of exemplary embodiments.

As mentioned above, a protective container can be used to protect fresh produce product while it is being transported from the packaging facility to a retail grocer and from the grocer to an end-user's kitchen. A protective container may also prolong the shelf-life of fresh produce product by isolating the contents from environmental factors that could cause damage or premature spoilage. In particular, the shelf-life of packaged produce including fresh lettuce can be extended if oxygen content is maintained between 1 percent and 9 percent. In particular, the integrity of the seal is critical to maintaining the desired oxygen level, and thus the shelf-life of packaged produce including fresh lettuce.

In packaging machines such as the VFFS discussed above that use sealing jaws to seal the protective container, seal integrity can be compromised by small foreign particles falling into the sealing area during sealing. The particles get caught in the sealing jaws potentially causing leaks in the seal. Leaks result in product-in-seal failures that cause the container to lose the desired internal conditions. The amount of foreign objects in the sealing area may be reduced by interrupting the constant flow of particles in the VFFS machine.

A flapper gate device can be used to modulate delivery of product to interrupt the flow of product into the polypropylene bag before it is sealed. Introducing a gate, however, adds mechanical components required to operate the gate into the flow path of the product, which increases the potential for metal objects to fall into the bag and contaminate the product. The flapper gate device described below reduces the potential for metal objects falling off the flapper gate and into the packaging. Techniques described herein provide similar performance to existing systems, while reducing or eliminating some of the problems.

In an exemplary embodiment described below, a flapper gate device coupled to the top or throat of a forming tube assembly is constructed using a single-piece stainless steel gate, which is relatively inexpensive to produce. Locating the flapper gate device at the top of the tube allows all removable metal parts required to operate the gate to be removed from inside the tube, which reduces metal contamination. The flapper gate device can also be removed and disassembled more easily outside the tube, which facilitates regular sanitation and maintenance operations.

A flapper gate provides more precise control over the flow of product than other gate configurations. The flapper gate can be controlled to provide real-time process feedback so that the VFFS system can be adjusted either manually or automatically. For example, the flapper gate may be pneumatically connected to an air piston or other device that actuates a pivot arm to open and close the assembly. A pneumatic control provides feedback to the VFFS system operator. The flapper gate is controlled by the packaging machine operator for optimum VFFS efficiency. Alternatively or additionally, the flapper gate control system can be adjusted to account for changes in packaging operation parameters including, for example, packaging speed.

1. Process for Packaging Produce Using a Flapper Gate Assembly

As mentioned above, a protective container, such as a polypropylene bag, can be used to preserve the quality of packaged produce product while it is being transported and stored before consumption. Polypropylene bags can be produced at a relatively low cost, and are generally compatible with high-volume automated packaging techniques. For example, VFFS machinery can be used to form a polypropylene film into a pocket or partially enclosed cavity in an automated fashion. A polypropylene film is fed into the machinery via a roll or sheet of material. The film is typically folded to form a partially enclosed cavity into which fresh produce can be loaded. In some cases, the partially enclosed cavity is sealed length-wise using a roll sealer to form a tube-shaped partially enclosed cavity. Once loaded with fresh produce, the formed cavity can be sealed on one or both ends using heat-sealing jaws to form a fully enclosed polypropylene bag.

Alternatively, other bag-filling machinery can be used to fill partially formed polypropylene bags with fresh produce in an automated or semi-automated fashion. For example, a polypropylene sleeve material can be used to create a partially enclosed cavity by sealing the sleeve at one end. Produce product can be placed in the partially enclosed cavity either manually or using automated machinery. The open end of the cavity can be sealed to form a fully enclosed polypropylene bag.

FIG. 1 depicts a flow chart of an exemplary process 100 for packaging produce product in packaged food containers. Process 100 may be part of one of the automated or semi-automated packaging process described above. FIGS. 2A-2C depict components used in one embodiment of exemplary process 100. For ease of explanation, the following example illustrates a process for packaging a leafy vegetable product (e.g., lettuce leaves) in a polypropylene bag. One of skill in the art would recognize that these techniques can be applied to other types of orientated polypropylene-polyethylene (OPP-PE) laminates, PE-Aluminum foil laminates, fresh produce products and other types of food containers.

In operation 110 of process 100, a produce product is loaded. As shown in FIG. 2A, produce product 210 is loaded into hopper 208 of packaging machine 200. The produce product 210 can be loaded into the hopper 208 either manually or using automated machinery. For example, produce product 210 may be fed into hopper 208 via a source feed tube or automatic weighing machine (not shown) located above the hopper 208. If operation 110 (FIG. 1) is implemented using VFFS packaging equipment, the produce product 210 is dropped from a chute above the hopper 208. As shown in FIG. 2A, produce product 210 is comprised of product particles of various sizes. FIG. 2A illustrates large produce particles 210A and small produce particles 210B. Although only large and small particles have been shown, one skilled in the art would recognize that the particle size can vary continuously between the size of the largest and smallest produce particles. As FIG. 2A also illustrates, the hopper 208 narrows to consolidate produce product 210 and funnel it into the top of tube 206.

As shown in FIG. 1, in operation 120, a partially enclosed container is filled with the produce product. Turning to FIG. 2A, packaging machine 200 is configured to wait for produce product 210 to fall through the length of tube 206 toward the opening 204 of the partially enclosed container 202. In some cases, the partially enclosed cavity 202 is placed or formed over a forming tube. For example, if operation 120 (FIG. 1) is implemented using VFFS packaging equipment, the partially enclosed cavity 202 may be formed around falling lettuce product and sealed at one end (the bottom end) using heat-sealing jaws 214. As shown in FIG. 2A, the partially enclosed cavity 202 has a cavity opening 204 shown as a dotted line. The cavity opening 204 may be near the location where the top of the partially enclosed cavity 202 is to be sealed using heat-sealing jaws 214 as described below with respect to operation 130 (FIG. 1) and FIG. 2C.

As shown in FIG. 2B, large produce particles 210A clump together and form an elongated charge of large produce product particles. On average, the large produce particles 210A fall faster and with less variation in speed than small produce particles 210B due to surface tension adhesion to the collating chute. Accordingly, when the majority of large produce particles 210A reach the middle of tube 206, many of the small produce particles remain in the hopper 208 or near the top of tube 206. The small produce particles are also more dispersed than the larger produce particles. Operation 120 (FIG. 1) continues until produce product 210 falls through opening 204 near the bottom of tube 206 and fills partially enclosed cavity 202. Because the packaging operation is performed in a substantially vertical orientation (i.e., with the cavity opening 204 facing upward), the produce product 210 typically settles toward the bottom of the partially enclosed cavity 202.

As shown in FIG. 1, in operation 130, the partially enclosed cavity is sealed to create a protective container. Turning to FIG. 2C, the partially enclosed cavity 202 may be placed so that cavity opening 204 is at or near heat-sealing jaws 214. The heat-sealing jaws 214 partially melt the package film material to create a seal. Other techniques, including adhesive bonding or mechanical fastening can also be used to seal the partially enclosed cavity 202.

FIG. 2C illustrates the spatial distribution of produce product 210 inside packaging machine 200 at the time partially enclosed cavity 202 is sealed. Produce particles 210 do not enter the partially enclosed cavity 202 all at once. Some of the produce particles initially loaded into the hopper fall behind the main charge due to variations in size and density as discussed above. As shown, both large particles 210A and small particles 210B are in the opening 204 of the partially enclosed cavity 202 when the cavity is sealed. Large particles 210A get caught in the heat-sealing jaws 214 because, although a sufficient amount of produce has been loaded to fill the cavity, the large particles fall in an elongated stream. Small particles 210B also fall into the sealing jaws because they drop at a slower speed and lag behind the majority of large particles.

Because of the elongated stream of large particles and the dispersed, slower falling small particles, there is rarely a break in the flow of product through the cavity opening. As a result, produce particles interfere with the sealing operation and prevent a clean seal from being made. If enough product gets caught in the sealing jaws, a product-in-seal failure occurs, which causes the container to leak and lose the desired internal conditions. Additionally, the package must be reworked to discard the failed bag and salvage the lettuce leaves. A one percent savings in product-in-seal packages may be worth approximately $900,000 per year.

FIG. 3 depicts a flow chart of an exemplary process 300 for reducing the amount of lettuce particles in the seal of a packaged food container by using a flapper gate. A flapper gate is preferable to other types of gates. For example, a horizontal sliding gate can crush product against the side of the tube when the gate is closed causing a sanitation issue. An angled flapper gate can provide better control over the flow of product and reduce the potential for damaging product. Process 300 may be part of one of the automated or semi-automated packaging processes described above. FIGS. 4A-4C depict components used in one embodiment of exemplary process 300 where produce particles such as lettuce are substantially prevented from interfering with the sealing operation. For ease of explanation, the following example illustrates a process for packaging a leafy vegetable product (e.g., lettuce leaves) in a polypropylene bag. One of skill in the art would recognize that these techniques can be applied to other types of orientated polypropylene-polyethylene (OPP-PE) laminates, PE-Aluminum foil laminates, fresh produce products and other types of food containers.

The mechanics of operation 300 may vary depending on the packaging machinery being used to package the produce. As shown in FIG. 4A, in the present embodiment, the flapper gate 416 is located at the top of a tube 406. In the present embodiment, an actuating mechanism controls the flapper gate inside the tube 406.

In some cases, the partially enclosed cavity 402 is placed or formed over a forming tube 406. For example, if a VFFS packaging operation is used, the partially enclosed cavity 402 may be formed around falling lettuce product and sealed at one end (the bottom end) using heat-sealing jaws 414. In a typical VFFS packaging operation, the flapper gate assembly 416 opens and closes to regulate the flow of product through tube 406 while the partially enclosed cavity 402 is formed from a continuous sheet of packaging film. As shown in FIG. 4A, the partially enclosed cavity 402 has a cavity opening 404 shown as a dotted line. The cavity opening 404 may be near the location where the top of the partially enclosed cavity 402 is to be sealed using heat-sealing jaws 414 as described below with respect to operation 360 in process 300 (FIG. 3).

As shown in FIG. 3, in operation 310 of process 300, a produce product is loaded. Turning to FIG. 4A, produce product 410 is loaded into the hopper 408. The produce product 410 can be loaded into the hopper 408 either manually or using automated machinery. For example, produce product 410 may be fed into hopper 408 via a source feed tube located above the hopper 408. If operation 310 (FIG. 3) is implemented using VFFS packaging equipment, the produce product 410 is dropped from a chute above the hopper 408. As seen in FIG. 4A, produce product 410 is comprised of product particles of various sizes. FIG. 4A illustrates large produce particles 410A and small produce particles 410B. Although only large and small particles have been shown, one skilled in the art would recognize that the particle size can vary continuously between the size of the largest and smallest particles of produce. As FIG. 4A also illustrates, the hopper 408 narrows in order to consolidate produce product 410 and funnel it into the top of tube 406. Alternatively, produce product may be loaded directly into the tube without the use of a hopper.

As shown in FIG. 3, in operation 320, the produce product is collected on the flapper gate. Turning to FIG. 4A, large particles 410A settle on flapper gate 416 while the slower falling small particles 410B continue to fall into hopper and accumulate on top of the larger particles 410A. By allowing both large and small particles to settle on the flapper gate 416, a condensed mass of produce is formed that can be released down the tube into the partially enclosed cavity 402. As shown in FIG. 4A, when closed, flapper gate 416 forms approximately a 45 degree angle with the vertical walls of tube 406. When the flapper gate is closed, it preferably forms an angle between approximately 35 degrees and 55 degrees with the vertical walls of the tube.

As shown in FIG. 3, in operation 330, the flapper gate is opened. Turning to FIG. 4B, the produce particles 410 that accumulated on the flapper gate 416 fall through tube 406 as a condensed charge. Allowing the produce product to accumulate on the flapper gate 416 at the top of the tube 406 before opening the flapper gate 416 creates a more compact charge of produce compared to the elongated charge in process 100 (FIG. 1). The flapper gate 416 may remain open for a fixed duration. For example, the flapper gate may remain open based on the amount of accumulated produce or to accommodate different packaging speeds. The amount of time that the flapper gate remains open may also vary based on the density of the product being packaged. The flapper gate may remain open long enough for the accumulated mass of produce particles to clear the lower tip of the flapper gate.

As shown in FIG. 3, in operation 340, the flapper gate is closed. Turning to FIG. 4C, after the large particles 410A have cleared the tip of the flapper gate 416, the flapper gate is closed. Closing the flapper gate 416 stops the flow of particles and prevents slower-falling small particles that had yet to accumulate on the flapper gate 416 from falling though the tube 406. Closing the flapper gate 416 provides for time delay of product to interrupt the trailing edge of the lettuce charge initially deposited into the hopper 408. Accordingly, closing the gate stops the continuous stream of lingering particles illustrated in FIG. 2C, and creates a distinct separation between charges of released produce.

As shown in FIG. 3, in operation 350, the partially enclosed cavity is filled with produce product. Turning to FIG. 4C, packaging machine 400 is configured to wait for the produce particles that cleared the flapper gate to fill the partially enclosed cavity 402. Again, on average, the large produce particles 410A fall faster and with less variation in speed than small produce particles 410B. However, by using the flapper gate 416 according to the operations described above, the charge of large particles 410A entering the partially enclosed cavity is more compact and the flow of small particles 410B following the main charge is cut off by closing the flapper gate 416. Accordingly, there are fewer produce particles 410 in the sealing area when the partially enclosed cavity 402 becomes full. Because the packaging operation is performed in a substantially vertical orientation (i.e., with the cavity opening 404 facing upward), the produce product 410 typically settles toward the bottom of the partially enclosed cavity 402. Operation 350 (FIG. 3) continues until produce product 410 falls through the opening 404 of the partially enclosed cavity 402 near the bottom of tube 406 and fills partially enclosed cavity 402.

As shown in FIG. 3, in operation 360, the partially enclosed cavity is sealed. Turning to FIG. 4C, once partially enclosed cavity 402 is filled with produce product 410, the partially enclosed cavity 402 is sealed to create a protective container. The partially enclosed cavity 402 may be placed so that cavity opening 404 is at or near heat-sealing jaws 414. The heat-sealing jaws 414 partially melt the package film material to create a seal. Other techniques, including adhesive bonding or mechanical fastening can also be used to seal the partially enclosed cavity 402. In some cases, it may not be necessary to form a completely air-impermeable seal. As a result of operation 360 (FIG. 3), a fully enclosed bag of produce product 410 is produced.

FIG. 4C illustrates the spatial distribution of produce product 410 inside packaging machine 400 at the time partially enclosed cavity 402 is sealed. As shown, the amount of produce particles in the opening 404 of the partially enclosed cavity 402 when the cavity is sealed is significantly reduced compared to FIG. 2C. In FIG. 4C, substantially all of the large produce particles 410A have cleared the sealing jaws, and only a few of the slowest-falling small particles potentially get caught in the heat-sealing jaws 414 and interfere with the sealing operation.

Variations of process 300 shown in FIG. 3 are possible. For example, the flapper gate may be opened prior to loading product such that the product passes though the tube without settling on the flapper gate. The flapper gate may be closed after the majority of the loaded product has cleared the flapper gate to stop the flow of slower-falling small particles and to prevent them from interfering with the sealing operation.

Additionally, when process 300 (FIG. 3) is used to package cut lettuce, it is advantageous to deliver the produce product at a high flow rate so that the partially enclosed cavity is packaged rapidly. For cut lettuce, the flow rate is typically adjusted to achieve a packaging rate between 55 and 65 bags per minute (BPM). The product flow rate is at least partially dependent on the speed of the packaging operation and the potential for the cut lettuce to string out as seen in the elongated charge in FIG. 1C at higher packaging rates, which causes higher potential for product-in-seal failures. If the packaging operation is implemented using VFFS packaging equipment, the product flow rate can be dependent on the bag feed rate. Typically, if the bag feed rate is increased, the product-in-seal failure rate will also increase because there is less time for the product to settle and less separation between charges. Conversely, the bag feed rate can also be reduced to decrease product-in-seal failures.

The flow rate may also depend on the type of produce being packaged. Packaging operations for produce that is whole leaf or has a smaller cut size require lower packaging rates. Lower rates are required to account for the greater variation in the speed at which produce particles of these types fall into the partially sealed container. Conversely, packaging rates may be increased for produce that is wet or denser, as there is less variance in the rate at which product particles fall.

Feedback in the packaging operation can be implemented manually by a package machine operator. In some cases, the feedback will be used to maintain product-in-seal failure rates within a specified range. The specific range and target values vary depending on the produce product being packaged. Lettuce and salad mix products may have a target product-in-seal failure rate as low as 2 percent and as high as 10 percent.

2. Flapper Gate Assembly

FIG. 5 depicts one embodiment of a flapper gate assembly 500 located at the top of a forming tube assembly 506. Flapper gate assembly 500 could be used in exemplary process 300 (FIG. 3) to regulate the product flow through the forming tube in order to achieve the characteristics described above and other desired system characteristics. The exemplary flapper gate assembly is also configured to eliminate any removable metal coupling attachments or mechanisms from the inside of the forming tube 406 (FIG. 4A) to reduce the potential for metal contamination in the sealed package.

The flapper gate assembly 500 depicted in FIG. 5 includes a linkage assembly 510, a pivot assembly 520, and flapper gate 530.

Linkage assembly 510 includes bracket 514 and linkage arm 512. Bracket 514 is attached to the outside of the junction between hopper 508 and forming tube 506. The flapper gate assembly 500 is attached to the outside of the top of tube 506 via bracket 514. Linkage arm 512 is connected to the bracket 514 in a fixed position relative to the tube 506.

The pivot assembly 520 is adapted to pivot without removable metal coupling attachments inside the tube 506. It includes actuator 522, piston rod 524, pivot arm 526, and hinge 528. Hinge 528 is attached to linkage arm 512 and is located at the intersection of the bracket 514 and tube 506. Actuator 522 drives piston rod 524, which is attached to pivot arm 526. Actuator 522 is attached to linkage arm 512 such that when actuator 522 is activated, force is transferred from linkage arm 512 to pivot arm 526 via actuator 522 and piston rod 524. Actuating piston rod 526 rotates pivot arm 526 around hinge 528.

In the present embodiment, the flapper gate 530 is pneumatically connected to the actuator 522 via piston rod 524 and the pivot arm 526 to open and close the assembly. Flapper gate 530 is connected to pivot arm 526 via hinge 528. Because the pivot assembly 520 contains all the removable parts, flapper gate 530 can be positioned in the tube 506 to regulate product flow to a sealing area without introducing removable parts inside the forming tube 506. For example, the flapper gate 530 may consist of a single piece of metal shaped such that forming tube 506 is nearly completely closed when the flapper gate 530 is positioned at an approximately 45 degree angle with respect to the vertical wall of the tube 506. When closed the flapper gate preferably forms an angle between approximately 35 degrees and 55 degrees with the vertical wall of the tube. When the flapper gate is fully open, it may form an angle of approximately zero degrees with the vertical wall of the tube.

The flapper gate 530 depicted in FIG. 5 is designed for use in a VFFS packaging operation. The size and shape of flapper gate 530 may vary depending on the size of the bag and the specific packaging equipment used to fill the bag. For example, the size and shape of the gate may conform to the shape of the tube when the flapper gate is in an open configuration. In some embodiments, the flapper gate is stainless steel and has a thickness of approximately 16 gage.

Locating the flapper gate assembly at the top or throat of the forming tube assembly has several advantages. First, it allows all removable parts to be located outside the forming tube. A gate located in the mid-to-lower portion of the tube would require an internal mechanism to operate the gate. An internal mechanism introduces connecting rods or bolt attachments that can come loose and fall into packaged product causing metal contamination. Compared to systems without gates, gate systems having removable parts inside the forming tube have been shown to produce 30 percent of the total metal contamination due to metal parts falling off the system. Because the described flapper gate assembly has no removable parts inside the forming tube assembly, it eliminates the possibility of metal contamination, thus reducing total metal contamination by 30 percent.

Locating all removable parts of the flapper gate assembly outside the forming tube also makes the assembly amenable to sanitation and cleaning. Any debris or produce product that accumulates on the assembly does not enter the packaged product because it is outside the tube. Also, the assembly is less likely to collect product debris and become dirty because it is not in the product flow path.

Locating the flapper gate assembly at the top of the forming tube assembly also allows the produce product to accumulate at a higher distance above the opening of the packaging. This allows the released charge of produce product to achieve greater velocity when entering the partially enclosed cavity. Higher velocities can compress the produce towards the bottom of the partially enclosed cavity as it enters the packaging. Compression of the product allows the desired amount of produce to fit into the cavity without the product on top interfering with the sealing jaws.

3. System Testing and Results

The performance of a device having a flapper gate assembly was compared to a control device that did not include a flapper gate assembly. In both devices, produce was fed into the top of a forming tube assembly and packaged using a VFFS machine. The control device was operated according to process 100 described in FIG. 1. The device having a flapper gate assembly was operated according to process 300 described in FIG. 3, where a gate device inside the tube was opened and closed to interrupt the continuous flow of product as shown in FIGS. 4A-C. With the exception of the flapper gate assembly, the control device and flapper gate device were the same in all respects.

The tests were conducted at the Soledad, California production facility. Tests were conducted for three different lettuce products: baby spinach, classic iceberg, and shred iceberg. The baby spinach was packaged at a rate of 50 bags per minute. The classic iceberg and shred iceberg were packaged at a rate of 60 bags per minute. The average rate for all products was 55 bags per minute.

The tests were designed to determine whether the performance of the flapper gate assembly met or exceeded the performance of existing designs. As shown in FIG. 6 and discussed below, the flapper gate assembly provides significant performance advantages with regard to reduced product-in-seal package failures.

Example 1 Product-In-Seal Rates in Produce Packaging Devices

FIG. 6 depicts testing results comparing a packaging device having flapper gate assembly to a control device without a flapper gate assembly. As an indicia of performance, the number of occurrences where lettuce product was caught in the sealing jaws were recorded.

With regard to FIG. 6, the columns designated “# PIS” represent the recorded number of product-in-seal failures, the columns designated “# Tested” represent the number of packages tested, and the columns designated “% PIS Leaker” represent the percentage of tested packages that experienced product-in-seal failures resulting in leaking packages. The values shown in the columns designated “n1”, “n2”, “p1”, “p2”, and “Pi Hat” are the number of tested packages formed by the flapper gate device, the number of tested packages formed by the control device, the percentage of product-in-seal failures for the flapper gate device, the percentage of product-in-seal failures for the control device, and the overall percentage of product-in-seal failures for both devices, respectively. The columns designated “z test” represent the z values in z-test analyses, where |z|≦1.96 indicates that the percentage of product-in-seal failures for the flapper gate device is not significantly different at the 0.05 confidence level. Devices having different letters in the columns designated as “SD” are significantly different at the 0.05 confidence level according to the z-test analysis. The column designated “% Reduction” represents the reduction in product-in-seal failures resulting from using the flapper gate assembly.

As shown in FIG. 6, for baby spinach lettuce, 8.33 percent of tested containers packaged using the control device without a flapper gate assembly had product-in-seal failures that resulted in leaking packages. This is compared to 3.65 percent of tested containers packaged using a flapper gate assembly. Accordingly, the flapper gate assembly resulted in a 56.2 percent reduction in product-in-seal failures for baby spinach. The z-test value of −17.4432 is less than −1.96, which indicates that the product-in-seal failure rates are statistically different at the 0.05 confidence level.

For classic iceberg lettuce, 5.41 percent of tested containers packaged without using a flapper gate assembly had product-in-seal failures that resulted in leaking packages. This is compared to 2.88 percent of tested containers packaged using a flapper gate assembly. Accordingly, the flapper gate assembly resulted in a 46.77 percent reduction in product-in-seal failures for classic iceberg. The z-test value of −8.3437 is less than −1.96, which indicates that the product-in-seal failure rates are statistically different at the 0.05 confidence level.

For shred iceberg lettuce, 5.34 percent of tested containers packaged without using a flapper gate assembly had product-in-seal failures that resulted in leaking packages. This is compared to 3.37 percent of tested containers packaged using a flapper gate assembly. Accordingly, the flapper gate assembly resulted in a 36.95 percent reduction in product-in-seal failures for shred iceberg. The z-test value of −5.9612 is less than −1.96, which indicates that the product-in-seal failure rates are statistically different at the 0.05 confidence level.

When averaging the three types of products, 6.77 percent of tested containers packaged without using a flapper gate assembly had product-in-seal failures that resulted in leaking packages. This is compared to 3.38 percent of tested containers packaged using a flapper gate assembly. Therefore, although the data in FIG. 6 indicate that the type of product and cut size can affect the percentage of product-in-seal leaker packages, overall the flapper gate device was able to reduce product-in-seal package failures by 50.1 percent in over 30,000 bag evaluations, as compared to the control device. And again, the z-test value of −19.4984 is less than −1.96, which indicates that the product-in-seal failure rates are statistically different at the 0.05 confidence level.

As shown in FIG. 6, there is some variation in the results due to a number of factors for the different products. For example, the time of year in which the lettuce is harvested may affect the leaf structure resulting in different leaf weights. This in turn may affect the product-in-seal failure rate as lighter leaves are more prone to arrive late in the sealing area and get caught in the sealing jaws of the packaging equipment. Lettuce harvested in the winter months from Yuma, Ariz. and processed at the Soledad facility is typically dense tissue growth. Lettuce in the summer months from the Salinas Valley in California has a thinner leaf from rapid heat-induced growth than the lettuce from Yuma. Therefore the lettuce from the summer months tends to be lighter which leads to increased product-in-seal failures. Additionally, the optimum open and close times of the flapper gate may vary based on the density of the product being packaged. Manual operator settings may be adjusted to account for differences in leaf density. As such, variance in packaging machine operator techniques and skills to overcome the density differences can also affect the results.

Example 2 Metal Contamination in Produce Packaging Devices

A review of metal contamination results shows that flapper gate assemblies located in the mid-to-lower portion of the forming tube were used in 15 percent of VFFS machines but contributed 30 percent of the metal contamination due to nuts, bolts and other metal parts falling off the linkage assembly that drives the flapper gate. Because the flapper gate assembly had no removable parts inside the forming tube, it reduced total metal contamination by 30 percent.

The foregoing descriptions of specific embodiments have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and it should be understood that many modifications and variations are possible in light of the above teaching. 

We claim:
 1. A system for reducing metal and product-in-seal contamination in a package of produce product, the system comprising: a tube positioned substantially vertically, the tube having a top, bottom, inside, and outside; a partially-enclosed cavity for containing the produce product, the partially-enclosed cavity having a cavity opening positioned below the bottom of the tube; a flapper gate assembly, connected to the top of the tube, comprising a linkage assembly, a pivot assembly, and a flapper gate, the linkage assembly having a bracket attached to the outside of the tube and a linkage arm connected to the bracket in a fixed position relative to the tube; the pivot assembly positioned outside the tube and attached to the linkage arm, the pivot assembly comprising an actuator, a piston rod, a pivot arm, and a hinge, wherein the actuator is configured to drive the piston rod, and the piston rod is connected to the pivot arm, which rotates around the hinge when the piston rod is driven; and the flapper gate positioned inside the tube and connected to the pivot arm via the hinge, wherein the flapper gate is configured to rotate around the hinge when the pivot arm is rotated to regulate product flow in the tube; and a sealing assembly configured to seal the partially-enclosed cavity to form a fully-enclosed package.
 2. The system of claim 1, wherein the flapper gate assembly is connected to a vertical form, fill, and seal (VFFS) machine.
 3. The system of claim 1, wherein the package is a polypropylene bag.
 4. The system of claim 1, wherein the flapper gate is a single-piece stainless steel gate.
 5. A system for reducing metal and product-in-seal contamination in a package of produce product, the system comprising: a tube having a top and bottom; and a flapper gate assembly, connected to the top of the tube, comprising a pivot and a flapper gate, the pivot positioned outside the tube; and the flapper gate positioned inside the tube and connected to the pivot, wherein the flapper gate is configured to regulate product flow in the tube by rotating around the pivot when the pivot is rotated.
 6. The system of claim 5, wherein the flapper gate assembly is connected to a vertical form, fill, and seal (VFFS) machine.
 7. The system of claim 5, wherein the package is a polypropylene bag.
 8. The system of claim 5, wherein the flapper gate is a single-piece stainless steel gate.
 9. A flapper gate device for reducing metal contamination in a package of produce product, the flapper gate device comprising: a linkage assembly having a bracket and a linkage arm connected to the bracket in a fixed position relative to the bracket; a pivot assembly attached to the linkage arm, the pivot assembly comprising an actuator, a piston rod, a pivot arm, and a hinge, wherein the actuator is configured to drive the piston rod, and the piston rod is connected to the pivot arm which rotates around the hinge when the piston rod is driven; and a gate connected to the pivot arm via the hinge, wherein the gate is configured to rotate around the hinge when the pivot arm is rotated, wherein the flapper gate device is configured to connect to the top of a tube such that the pivot assembly is outside the tube and the gate is positioned inside the tube to regulate the flow of the produce product through the tube.
 10. The flapper gate device of claim 9, wherein the flapper gate device is connected to a vertical fill-form-seal (VFFS) machine.
 11. The flapper gate device of claim 9, wherein the package is a polypropylene bag.
 12. The flapper gate device of claim 9, wherein the gate is a single-piece stainless steel gate.
 13. A method of reducing metal and product-in-seal contamination in a package of produce product, the method comprising: loading the produce product into a tube; opening a flapper gate located at the top of the tube to allow the produce product to flow through the tube into an opening of a partially-enclosed cavity positioned below the tube; closing the flapper gate to stop the flow of produce product through the tube; and sealing the partially-enclosed cavity to produce a fully-enclosed package containing the produce product.
 14. The method of claim 13, further comprising collecting the produce product inside the tube using the flapper gate.
 15. The method of claim 13, wherein the partially-enclosed cavity is sealed when the partially-enclosed cavity is determined to be full.
 16. The method of claim 13, wherein the method is implemented as part of a vertical fill-form-seal (VFFS) packaging operation.
 17. The method of claim 13, wherein the package is a polypropylene bag.
 18. The method of claim 13, wherein the flapper gate is a single-piece stainless steel gate.
 19. The method of claim 13, wherein opening the flapper gate occurs before loading the produce product into the tube.
 20. The method of claim 13, wherein loading the produce product into the tube occurs before opening the flapper gate. 